1. Technical Field
This disclosure relates generally to an engine starting system equipped with, for example, a starter and an electronic control unit (ECU), and more particularly to such a system designed to minimize mechanical noise generated when a pinion is moved in a straight line and then contacts with a ring gear of an engine.
2. Background Art
Typical engine starting systems for internal combustion engines are equipped with an electric motor, a starter, and an electronic control unit (ECU). The electric motor works to produce torque for starting the engine. The starter is equipped with an electromagnetic relay which energizes or deenergizes the electric motor and also moves a pinion straight to a ring gear coupled to the engine. The ECU works to control the operations of the starter.
Specifically, the electromagnetic relay produces a magnetic attraction to move the pinion in an axial direction thereof into contact with the ring gear and then mesh the pinion with the ring gear. The mechanical noise is, therefore, created upon the contact of the pinion with the ring gear. Such a noise will also be referred to herein as an axial impact noise.
With the growth of hybrid vehicles or automotive idle stop systems (also called automatic engine start/restart system), there is an increased demand for quietness in the vehicles. Measures against the axial impact noise are, therefore, called for.
Japanese Patent First Publication No. 2003-083212 teaches an engine starting system which works to start actuating an electric motor at a low speed simultaneously with start of thrusting a pinion toward a ring gear coupled to the engine and then rotate the electric motor at a high speed to start the engine after the pinion meshes with the ring gear completely. This system serves to reduce mechanical noise (which will also be referred to as a radial impact nose below) arising from contact of a tooth plane of the pinion with that of the ring gear, but however, it is not engineered to reduce the axial impact noise.